feat: add Alibaba FC3 serverless runtime provider support

Add comprehensive support for Alibaba Cloud Function Compute 3.0 (FC3)
as a sandbox runtime provider, enabling serverless deployment of ROCK
sandboxes with three deployment modes:

- Custom Runtime: Lightweight Python runtime with bootstrap script
- Custom Container: Full Docker container deployment
- Hybrid Adapter: HTTP/WebSocket adapter for FC3 function integration

Key components:
- FC3 client with thread-safe CircuitBreaker for fault tolerance
- WebSocket reconnection and retry mechanisms
- Path traversal protection in server
- Session affinity configuration (HEADER_FIELD mode)
- Comprehensive test coverage (78 tests)

Change-Id: I757e00577a16c6dbbec1f65e09dbd0159c3579a4
Co-developed-by: Claude <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: 世如

rock-conf/rock-fc3.yml

@@ -0,0 +1,25 @@
+# =============================================================================
+# ROCK Admin 运行时配置 - FC3 环境
+# =============================================================================
+#
+# 用途：ROCK Admin 服务启动时加载的运行时配置
+#
+# 使用方式:
+#   rock admin start --env fc3
+#   或 export ROCK_CONFIG=rock-conf/rock-fc3.yml
+#
+# 注意：此文件不是函数部署配置，FC3 函数部署使用
+#   rock/deployments/fc3_rocklet/*/s.yaml + s deploy
+#
+# =============================================================================
+
+# Ray 配置（FC3 环境不使用 Ray）
+ray:
+    runtime_env:
+        working_dir: ./
+        pip: ./requirements_sandbox_actor.txt
+    namespace: "rock-sandbox-fc3"
+
+# 预热配置（FC3 环境无本地镜像需预热）
+warmup:
+    images: []

rock/actions/sandbox/request.py

@@ -44,6 +44,8 @@ class BashAction(BaseModel):
 class WriteFileRequest(BaseModel):
     content: str
     path: str
+    encoding: str = "utf-8"
+    """Text encoding to use when writing the file. Defaults to utf-8."""
 
 
 class CloseBashSessionRequest(BaseModel):